Numerical display using plural light sources and having a reduce

Details Numerical display using plural light sources and having a reduce Numerical display using plural light sources and having a reduce

1977-06-06

1980-04-15

Trafton, David L.

Communications: electrical

Land vehicle alarms or indicators

Internal alarm or indicator responsive to a condition of the...

368241, 340762, 340782, G09F 932

Patent

active

041986296

ABSTRACT:
The present invention relates to a numerical display having a reduced dc current requirement per character display site. The invention is applicable to a variety of numerical displays including seven segment and 4.times.7 matrix displays using light emitting diodes, and low voltage incandescent segmented units designed to replace light emitting diode displays. A practical application is for displaying time in an ac powered clock or clock radio in which it is desirable to keep the dc current requirement of the display to a substantially constant minimum suitable for use with a low cost, transformerless power supply conventional with radio receivers. The current requirement of a character display site is reduced over that of full parallel operation by selectively serializing certain light sources in a manner leaving the display control circuitry uncomplicated by permitting each light source state to be controlled by a shunt control switch sharing a common bus. Since a seven segment display may assume 2.sup.7 or 128 characters and only 10 (or 11) characters are used in a full numerical font, considerable control flexibility may be sacrificed by serial segment connection before any useful characters are eliminated. A display site having a full numerical font may be reduced from 7 to 4 branches and its current reduced 43% relative to full parallel operation under shunt control. Shunt control, which diverts, rather than prevents, current flow in the display, permits the display current to remain substantially constant irrespective of the numbers displayed. When the dc current drain of a time display is comparable to that of a radio and the ac component is tolerably low, the two may be serially connected without substantially increasing the dissipation over that of the clock or the radio alone.

REFERENCES:
patent: 3146436 (1964-08-01), Crow
patent: 4017847 (1977-04-01), Burford et al.
patent: 4052842 (1977-10-01), Beguin et al.

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